Imaging systems able to control the X-ray source output are known to exist, in particular the use of automatic exposure control (AEC) is available on many systems to avoid over exposure. See for example D. B. Plewes, E. Vogelstein, ‘A scanning system for chest radiography with regional exposure control: Practical implementation’, Medical Physics, volume 10 number 5, 655-663, 1983.
Similarly, computed tomography (CT) systems adjust the exposure at each view to ensure the dynamic range of response of the detector array is used most efficiently, as set out in L. Jangland, E. Helmius, ‘Automatic exposure control on CT systems’, Radiology, volume 201, 792S, 1996, U. Nyman, T. L. Ahl, M. Kristiansson, L. Nilsson, S. Wettemark, ‘Patient-circumference-adapted dose regulation in body computed tomography. A practical and flexible formula’, Acta Radiologica, volume 46 number 4, pages 396-406, 2005, and T. H. Mulkens, P. Bellinck, M. Baeyaert, D. Ghysen, X. Van Dijck, E. Mussen, C. Venstermans, J. L. Termote, ‘Use of an automatic exposure control mechanism for dose optimization in multi-detector row CT examinations: Clinical evaluation’, Radiology, volume 237 number 1, 213-223, 2005.
A chest radiography scanning system has been described by Odelft, whereby the radiation intensity distribution is adapted to ensure optimum exposure at all points. This system is described in H. Vlasbloem, L. J. Schultze Kool, ‘AMBER: A Scanning Multiple-Beam Equalization System for Chest Radiography’, Radiology, volume 169, 29-34, 1988.
A mammography system has also been proposed, which would use information gained from the leading edge of a scanning beam to modify the scan velocity in M. Åslund, B. Cederström, M. Lundqvist, M. Danielsson, ‘AEC for scanning digital mammography based on variation of scan velocity’, Medical Physics, volume 32 number 11, 3367-3374, 2005.